This invention relates to an evaporation cooled gas insulated electrical apparatus and more particularly, improvements of cooling efficiency of the electrical apparatus and reduction in size and weight of a condenser in the electrical apparatus.
In conventional electric devices such as a transformer, the so-called evaporation cooled device is known in which a condensable refrigerant is used as a means for improving the dissipation efficiency of the heat generated from the interior of the device.
Referring to FIG. 1 showing an embodiment of the evaporation cooled device, an electric device 1 generating heat from the interior thereof is disposed in a tank 2 which is filled at a predetermined rate with an electrically insulating noncondensable gas 9 and an electrically insulating condensable liquid refrigerant 5 being capable of evaporating into vapor at an operating temperature of the electric device 1. A liquid pump 6 is connected to the top and bottom portions of the tank 2 through pipes 7 so as to pump the liquid refrigerant 5 collected on the tank bottom through the upper portion of the tank 2, thereby spraying the liquid refrigerant 5 on the electric device 1. A condenser 3 comprises upper and lower headers 4a and 4b respectively, a lower conduit 12 connecting the lower header 4b to the lower portion of the tank 2, an upper conduit 14 connecting the upper header 4a to the upper portion of the tank 2, and a plurality of upstanding cooling ducts 10 connected to the upper and lower headers 4a and 4b, respectively. The liquid refrigerant 5 sprayed on the electrical device 1 absorbes the heat, so that a part of the liquid refrigerant 5 evaporates into a vapor refrigerant 8. The noncondensable gas 9 and the condensable refrigerant 5 are chosen such that the specific weight of the vapor refrigerant 8 is greater than the specific weight of the noncondensable gas 9. Accordingly, the vapor refrigerant 8 flows downward and is collected in the tank lower portion, namely, a part of the vapor refrigerant 8 flows into the cooling ducts 10 through the lower conduit 12 and the lower header 4b. Since the cooling ducts 10 dissipates heat while being cooled by a fan 11 disposed near the condenser 3, the vapor refrigerant 8 is liquefied and the heat therefrom is dissipated at a rate corresponding to dissipating capacity of the condenser 3 whereby the refrigerant is utilized as a heat transfer medium. In such a cooling system, since the vapor refrigerant 8 flows downward, the noncondensable gas 9 is thereby forced upward due to the difference in the specific weights thereof, an interface 13 is formed between the vapor refrigerant 8 and the noncondensable gas 9 in the tank 2 and the condenser 3. Specifically, definite interface 13 is not easily formed in the tank 2, since the vapor refrigerant 8 is continuously generated in response to the heat generated in the electric device 1. However, the interface 13 is formed at the interface defined by the volume ratio of the vapor refrigerant to the noncondensable gas corresponding to the pressure within the tank 2. Since the tank 2 is communicated with the condenser 3 through the upper and lower headers 4a, 4b and the upper and lower conduits 14, 12, respectively, the interface 13 is located at a common level of H.sub.o in both the tank 2 and the condenser 3. The portion of the condenser 3 higher than the interface 13 is filled with the noncondensable gas 9 having a low rate of heat transfer, so that the cooling ducts 10 of the condenser 3 effectively dissipate heat only up to the interface level of H.sub.o. Accordingly, even when a large-sized condenser 3 is disposed for the electric device 1, it has the disadvantage in that the cooling efficiency of the cooling ducts is very low.